1. Field of the Invention
The present invention relates to an output information system for providing specific data signals from an interchangeable lens to a camera body for use by a microprocessor in the camera body without the need for addressing, such as by using gate arrays.
2. Description of the Prior Art
Prior art camera systems employing microprocessors in the camera body which receive information from camera accessories, such as interchangeable lenses or stroboflash devices, for use by the microprocessor in controlling the operation of the camera are well known in the art such as, by way of example, described in British Patent No. 1,552,597; U.S. Pat. Nos. 4,509,842; 4,477,164 and 4,560,267; and Japanese Patent Publication Nos. 54-108628 and 59-84228. All of these prior art systems, however, employ an addressable read only memory or ROM located in the lens or accessory for storing the preset information to be sent to the microprocessor. Because of the use of a ROM, many inherent disadvantages are present in these prior art systems, such as an inherent lack of flexibility due to the fact that a ROM by its very nature is unique to a given microprocessor, has a data content which is inherently fixed, and is inherently discretized in its data storage. In addition, an address circuit must inherently be employed with such a prior art ROM based system whether the addressing is done by the camera body or ultimately by the accessory, since the ROM requires an address and a table look-up function in order to obtain the data stored at a particular fixed location in memory. Furthermore, a ROM inherently requires a long lead time in manufacture and is costly to produce. These disadvantages of the prior art ROM systems are overcome by the gate array based system of the present invention.
In addition to the aforementioned prior art ROM based systems, there have been prior art camera systems which employ simple switches to provide digital information to a microprocessor for use by the microprocessor, such as disclosed in U.S. Pat. Nos. 4,104,649; 4,426,147 and 3,428,858; however, none of these prior art systems is capable of readily providing the sophisticated information that the gate array based system of the present invention can while, thus, providing many of the benefits of ROM based systems without providing any of the disadvantages, operating in a totally different manner.
As disclosed in Japanese Patent Publication No. 54-108628 and U.S. Pat. No. 4,560,267, by way of example, clock pulses are sent from the camera body microprocessor to the lens in order to cause an address to be generated by the lens to obtain data fixedly stored in the ROM with the data then being sequentially output serially back to the microprocessor. In the present invention, although clock signals sent from the microprocessor are utilized and information is serially sent back to the microprocessor, there is no generation of addresses, nor is there any address function employed.
Another example of a prior art interchangeable lens of the type employed with a camera having a microprocessor in the camera body is disclosed in Japanese Patent Laid-Open No. 84228/1984, in which an interchangeable lens is provided with a ROM that fixedly stores various data and with a circuit that produces address data for the ROM, with the data fixedly stored in the ROM being produced according to the address. However, this prior art device also requires an address data output circuit for the ROM, thereby resulting in complex construction and increased manufacturing cost. Moreover, in such prior art systems, in order to reduce size, the ROM is constructed in the form of a masked ROM consuming extended periods of time for development and increased amount of expenses. Though a P-ROM can be developed consuming reduced periods of time, it imposes a problem of increase in the size. These disadvantages of the prior art are overcome by the present invention. Moreover, although these disadvantages are overcome by the gate array arrangement of the aforementioned U.S. patent application entitled "Camera Accessory Output Information System", the system disclosed therein normally requires a decoder in addition to a counter to control the gate array, whereas the present invention does not require any such decoder.